Wind Levels

Surface to 1km Layer (SFC-1km) - Recent studies have suggested that vertical wind shear below the LCL may play an important role to low-level mesocyclonogenesis and tornado potential. LCLs below 1000m are also found to be correlated with tornadoes. Therefore, under conditions of low LCLs, shear parameters through this layer can be used to help evaluate tornado threat.

Surface to 3km Layer (SFC-3km) - This layer has been used for many years to estimate the inflow layer of thunderstorms. Depending on the environment, this may be too deep or too shallow. However, parameters such as bulk shear and helicity are commonly calculated for this layer.

Surface to 6km Shear (SFC-6km) - The bulk wind difference over 0-6 km AGL layer discriminates strongly between supercell and nonsupercell thunderstorm environments. The transition from nonsupercell to supercell thunderstorms occurs as the 0-6 km bulk wind difference increases from roughly 25 kt to 40 kt, with larger values favoring supercells.

Cloud Bearing Layer - The layer calculated by parcel theory to contain the thunderstorm updraft. The bounds of the layer are the LCL and EL of the most unstable parcel.

Lower Half Storm Depth - Defined as 50% of the vertical distance from the effective inflow base to the equilibrium level for the most unstable parcel in the lowest 300 mb.